The use of anion exchange membranes in diffusion dialysis for separating metal ion contaminants from the plating acid has been known for some time. U.S. Pat. No. 5,062,960 to Asahi Glass Company, Ltd., discloses an apparatus for recovering acid by diffusion dialysis using anionic exchange membranes. This patent discloses the need for cooling compartments disposed between each pair of adjacent membranes "A." The construction and the assembly as described in the cryptic disclosure of the '960 Patent, fails to teach any particular orientation of the anionic exchange membrane cells and of the means by which the fluids are caused to flow through the cells, although the cells are depicted in vertical or upright orientation. In essence, such methods have not been found generally effective for a variety of reasons related to the construction operation of the apparatus used to perform those methods.
Therefore, it is the object of this invention to provide an improved apparatus for separating metallic ions from contaminated acids which result in metal plating processes to achieve improved recovery rates without the necessity of cooling compartments whereby the material and environmental costs and the other costs and problems incident to the disposal of contaminated acids are virtually eliminated.
A further object of this invention is to provide an apparatus of the above type that is simple and effective in its operation which provides improved performance over the heretofore available apparatus for carrying out such processes.
Another further object of this invention is to provide an apparatus capable of recovering at generally uniform flow rates, a relatively uncontaminated acid from a contaminated or waste acid containing metal ions dissolved therein, such as result in metal plating processes whereby the recovered acid is adapted for repeated usage in metal plating processes.